[Asterisk-Users] How to start a playback after the called party picks up?

[Ronald Wiplinger]

1. I want to call somebody and, as soon (and not before) a playback 
should be played. How can I do that?
2. How can I accept dtmf tones with such calls?

Example:
System calls all staff and ask them a question. The staff will answer 
with a digit!
The playback should start when the staff picks up.